Archive for July, 2011

OperationCastle, is to detonate what is to be the second test of a new Hydrogen Bomb weapon on 1 March 1954. This test, code named Bravo Shot, is predicted to be a smaller version of an earlier 1952 first test of a Hydrogen Bomb design. This earlier test had been designated Mike shot of Operation Ivy. Mike was measured at about 10 Megatons yield, equal to 750 Hiroshima Atom Bombs in size. Bravo is expected to be less than half of that yield, and so the exclusion zone for safety is set at about 20 miles surrounding Bikini Atoll, in the Marshall Islands of the South Pacific.

Weather predictions on 28 February are downgraded to “unfavorable” to the test. Winds aloft at 20,000 feet are observed to be strong and moving towards Rongelap Atoll, a lightly populated area. Nevertheless, the decision is made to proceed. The Scientific Director of Operation Castle, Dr. Alvin C. Graves, has final authority over the military commander. Fallout predictions still indicate that the islanders will not receive a dangerous radiation dose. He makes the decision to continue the test. Joint Task Force 7 directs several observation ships to be relocated southward to accommodate the weather and avoid potential fallout.

At 06:45 hours in the pre-dawn darkness of March 1, Bravo Shot is detonated. Quickly the size of the fireball and rising cloud of debris

Bravo Detonation - Operation Castle

exceed all expectations of size and nuclear yield. Within milliseconds, Bravo assumes a destructive energy of unknown ferocity to the test designers. Within 10 minutes the cloud has topped 130,000 feet in height with a diameter of 62 miles.

A few weeks earlier, in mid-February 1954, in the Japanese port of Yaizu, Shinzuoka, a tuna fishing boat prepares to set out to sea. Her name is Daigo Fukuryū Maru, (The Lucky Dragon No. 5), and her crew of 23 rapidly readies for her excursion into the seas of the South Pacific. In the ensuing weeks, she then sails to a position about 40 miles to the east of Bikini Atoll, and, at dawn of March 1st, her crew is working at their nets, positioned well to the east of the announced test exclusion zone around Bikini.

Suddenly, the western sky lights up with a flash intensity brighter than the sun. Her crew shields their eyes in wonder at this unearthly event; some place their hands before their eyes, and are amazed that, in the flash brightness, they can see the bones of their fingers inside their flesh. Some nine minutes later the shock front arrives, traveling with a velocity of hundreds of miles per hour. The boat is lifted and shaken to its core. Frantically the crew clings to whatever rigging is available until the storm finally passes on. Somehow all survive and the boat seems able to navigate.

As they work, several hours later a white snow begins to drift from the sky. It is a fine white flaky dust (calcified choral) which tenaciously clings to everything; hair, arms, fingernails, the boat deck, nets, fish. Somewhat alarmed, the crew scoops it up with their bare hands and puts it into bags. The fallout continues for some three hours, as the crew recovers their nets and heads for home port, a journey which will take two weeks. The ash cannot be completely removed from the ship surfaces, and some remains for the length of the journey. The crew lives, breathes and eats with the white ash as a constant companion. One crew member puts some under his pillow and sleeps with it

Within a few hours some of the crew begin to experience nausea and loss of appetite, followed soon by vomiting. (The Gastro- Intestinal reaction is an early symptom of the Acute Radiation Syndrome.) Some experience headaches, and eyes begin to itch. Their skin and hands slowly itch and redden as if burned, throats swell and gums bleed. Later, the crew will refer to the white material as shi no hai – the death ash.

On March 14, Lucky Dragon arrives in port at Yaizu. Doctors are summoned and the crew is diagnosed with Acute Radiation Syndrome. They are rushed to two separate Tokyo hospitals. As weeks pass, some develop skin sores and experience temporary sterility. Reddened skin begins to turn dark from Beta burns, eyes and ears develop a runny discharge, some jaundice with swollen livers, red and white cell counts drop, as do platelets. Ship’s radioman Aikichi Kuboyama has an especially difficult time with breathing.

The nine ton fish catch from Lucky Dragon is shipped to market and consumed. Later catches from the area are found to be radioactive, and it is noted that the fallout into ocean waters provides a method for tracking ocean currents. A movement of outrage arises among the Japanese as they cry out against a “second Hiroshima”.

On September 23, 1954 radioman Aikichi Kuboyama dies of lung failure despite all efforts to save him. By this time, many of the crew are suffering from contracted Hepatitis due to transfusions of tainted blood. Scientists later calculate that crew doses ranged from 750 rem down to 200 rem. (A dose of 450 rem is sufficient to kill half of the exposed population.) However, some fourteen months later, all 22 members of Lucky Dragon are released from the hospitals. They face a future of increased likelihood of cancer.

Aikichi Kuboyama writes in his will that he hopes to be the last victim of Atomic and Hydrogen bombs. He became the first and hopefully the only Japanese to die from Hydrogen Bomb effects.

Castle Bravo shot is later measured at 15 megatons, the largest nuclear weapon ever exploded by the U.S. Later on, the Soviets will detonate a monster at 50 megatons, in a relentless cold-war battle of one-upmanship.

But the story of Castle Bravo does not end here. While the Lucky Dragon is enduring fallout, the cloud of radioactive fission products is drifting further into the Pacific, towards a native population living on Rongelap Atoll, a more distant part of the Marshalls. We continue their story next…

In the pre-dawn darkness of March 1, 1954, Operation Castle is located on the atoll of Bikini,and is quietly counting down to

The Lucky Dragon

detonate the second shot (code named Bravo Shot) in a series of nuclear weapons detonations. Bravo is to be the second test of a new kind of weapon, known as a Hydrogen Bomb. Unknown to all, drifting quietly about 40 miles to the east of the atoll, is a Japanese fishing boat named The Lucky Dragon. Her crew is working hard and is unaware they have penetrated the waters of the declared test exclusion zone.

Bikini Atoll, locatedin the South Pacific Marshall Islands chain, consists of a series of 23 islands surrounding a central deep lagoon of area about 230 square miles. By this time in 1954, the bottom of the Pacific is already a cluttered graveyard for many sunken ships from the U.S. Navy and the Japanese Navy. The ships were floated in the test areas eight years earlier in 1946 and then destroyed during a series of nuclear detonations code named Operation Crossroads. Previously the Marshall Islands were under Mandate of the Empire of Japan, but after World War II some of the islands had come under United States control as part of the Trust Territory of the Pacific Islands. Bikinibecame part of the Pacific Proving Grounds, and as such, became the site of more than 20 nuclear weapons tests between 1946 and 1958.

The Ivy Mike shot, in an earlier test series of November 1952, was the nation’s first test of a thermonuclear (Hydrogen) weapon. It was measured at about 10 megatons, or about 750 times more powerful than the Hiroshima Atomic Bomb. Mike vaporized an island and verified a bomb design known as the “Teller-Ulam”

Deuterium Tritium Fusion

design. Hydrogen weapons were long the dream of Edward Teller during development of the wartime A-Bomb at Los Alamos. Teller always referred to his concept for a hugely more powerful device as “The Super”, and he was constantly agitating Oppenheimer and the entire design team to begin developing the new concept. He said this weapon could be orders of magnitude more powerful than the Uranium-based A-Bomb.

The Hydrogen Bomb design utilized a different technique than did the A-bomb. Instead of fissioning heavy Uranium nuclei apart into smaller fragments, the H weapon used the same mechanism as in the Sun of our Solar System. This technique fused together light nuclei of Hydrogen isotopes, thereby releasing hugh amounts of binding energy. The reaction uses two forms of Hydrogen (called Deuterium and Tritium). These Hydrogen nuclei have one and two extra neutrons respectively. When they are mixed in a very high temperature environment such as exists on our own Sun, they fuse together to make Helium, and release a neutron with large amounts of energy. An additional somewhat positive side-effect is that there are very little radioactive “fission products” generated as fallout in this type of device (except of course for particles of debris sucked into the explosion.) The Hydrogen is put into the bomb in a chemical form of Lithium Hydride.

So, in our story, Teller finally gets his way, and Los Alamos proceeds to design and develop the new device. Teller works with

Teller/Ulam Bomb Design

another scientist named Stanislaw Ulam. One big problem arises in how to generate the extreme temperatures needed for the reaction to occur. The bomb has to burn as hot as the Sun or there will be no fusion reaction. Answer: put in an Atomic Bomb (actually two bombs) to set it off and generate enough high temperatures for fusion in the center of the massive explosion.

The first test, Ivy Mike, is conducted on Eniwetok in 1952, and it is successful. It seems to verify the Teller/Ulam concept. Except that, as noted earlier, there was a problem. Mike needed to keep its chemicals very cold before the blast – cryogenically cold in fact. So for the test, hugh amounts of refrigeration, gas tanks, cables, pumps, plumbing, electrical generators, etc. were needed just to keep the test at liquid cryogenic temperatures during countdown. Consequently, the Mike device was hugh and very cumbersome. No way could this thing ever be used as a weapon, let alone fit into the biggest aircraft. So all the cold liquids had to be eliminated if the H-bomb was ever to be used as a practical weapon.

Castle Bravo then,was the first test of the so-called “dry fusion” design. It used Lithium Deuteride instead of a mix of Deuterium and

The "Shrimp" H-Bomb

Tritium gas. No cryogenics; the device was still big (almost 11 tons), but perhaps small enough to fit into the biggest bombers. The assembly crew jokingly referred to the device as “the Shrimp”. (The photo has inserted the silhouette of a man for size comparison.)

Populating areas around the Southern Pacific test waters, the crew of the Lucky Dragon was also joined by small native populations in the Marshalls. Hundreds of natives lived peacefully on the atoll of Rongelap, consisting of 61 islands surrounding a lagoon of some 1000 sq miles. Rongelap lies about 73 miles from the Castle testisland. But there is no need for extra concern, since the Bravo shot is expected to be far smaller than the original Mike test of 10 megatons.

At 06:45 on March 1, 1945 the detonation takes place.

The Castle Bravo Blast

Surprisingly, the fireball generated in less than one second measures over 4.5 miles in diameter. It vaporizes a crater of 6,500 feet across, 250 feet deep, and the mushroom cloud rapidly rises to altitude. Within 10 minutes the cloud tops 130,000 feet, with a diameter of 62 miles. At this time the radioactive cloud is expanding with a frontal velocity of 224 miles per hour. The detonation seems to be assuming a destructive energy far greater than had been calculated by the test designers. Bravo later is measured to be more than 15 megatons, and is to become the largest thermonuclear detonation ever exploded by the United States…